Remotely controlled high energy discharge drive circuit



June 30, 1970 R. 1.. SCHAAF 3,518,656

REMOTELY CONTROLLED HIGH ENERGY DISCHARGE DRIVE CIRCUIT Filed April 7, 1967 6.2 7 TRANSWER TRANLSImSSION RECEIVER 24 I 4' f I y Z1 31 52 P o-u/4m. 2s

25 V 15 Z: P L g LOAD 30 25 if L 5 22 T M f FIG. 1

/NVENTOR ROBERT L. SCHAAF United States Patent 0 3,518,656 REMOTELY CONTROLLED HIGH ENERGY DISCHARGE DRIVE CIRCUIT Robert L. Sehaaf, Boulder, Colo., assignor to International Business Machines Corporation, Armonk, N.Y.,

a corporation of New York Filed Apr. 7, 1967, Ser. No. 629,124 Int. Cl. H04m 11/00 U.S. Cl. 340310 8 Claims ABSTRACT OF THE DISCLOSURE A controlled transistorized circuit that enables the transmission of high energy pulses to a remotely located load through the medium of charging a capacitor in a RC circuit configuration at a receiving terminal. Then remotely controlled switching discharges the capacitor into a load such as a print actuating solenoid of a printing device.

BACKGROUND OF THE INVENTION Field of the invention The invention is directed to the improvements and application of remotely controlled D.C. switching circuitry.

Description of the prior art In communication systems the energy which is transmitted by direct voltage switching is limited by line impedance of the communication lines and by the voltage and current restrictions imposed upon the common carriers by governmental agencies.

In the prior art, transistorized switching circuits which are particularly constructed for use in automobile ignition systems are available in various forms. In these prior art circuits, the breaker points of an automobile ignition system drive an input or control electrode of a semiconductor device, resulting in very small switching current requirements. A circuit particularly adapted for use in ignition systems may advantageously employ an inductor which is connected in series with a voltage supply and a switching device such as a transistor. When the control device is switched on, current builds up in the inductor to create a magnetic field around the inductor so as to charge the inductor. Then, when the control device is switched olf, the current tends to continue thereby generating a pulse of current when the inductive field collapses. A capacitor may be arranged in the circuit to be charged by this inductive current pulse. The primary winding of an ignition coil may be placed in the discharge path of the capacitor such that a sharp voltage spike upon discharge of the capacitor is generated in the secondary of the ignition coil for operatively driving the spark plugs.

However, such switching circuits do not readily lend themselves to switching applications in data transmission systems wherein it has become desirable to operate unattended printing devices at points which are remotely located with respect to the controlling data processor. Varying impedances due to differences in distances between the transmitting terminal and the unattended receiving terminal must be taken into consideration. There are other restrictions in such data communication systems due to voltage and current restrictions imposed upon the communication carriers.

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SUMMARY OF THE INVENTION Accordingly, it is a primary object of the present invention to provide switching arrangements of the type utilizing a controlled transistor device adapted to control the charging of a capacitor in an RC circuit and subsequently switch the circuit so as to discharge the capacitor into the print actuating solenoid of a printing device. The invention is particularly directed to the circuit configuration for accomplishing remote charging and discharging into a load through the employment of unique remote controlled switching techniques.

An advantage is attributable to the basic fact that no local source of power is required at the remote terminal, hence, the capacitor becomes a power supply. A further advantage resides in the fact that only a two-wire transmission line is necessary to effect control. Automobile ignition type schemes are not suited as transmission line drivers in that they would require a three-Wire line for remote control.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, this circuit enables the transmission of higher energy pulses to a remote load than is possible by conventionally switching a voltage source at the transmitter station. The energy transmitted by direct voltage switching is limited by line impedance and voltage and current restrictions. The principle of the high energy line driver is to charge the capacitor .19 at the receiving station by direct voltage switching, then to discharge it across the load 13. With reference to FIG. 1, there is shown the circuit configuration for accomplishing remote charging and local discharging of the capacitor 19. Between drive pulses the base of transistor 10 is negative; accordingly, transistor 10 is in its conductive state and the capacitor 19 will charge to approximately the voltage of VI through the impedances Z1 and Z2, the resistance 18 and diode 12. To initiate a drive pulse, the base of transistor 10 is made positive so as to bias transistor 10 to a cut-off condition. The transmission lines 14 and 15 are now open circuited such that the voltage V1 no longer provides a charging potential to capacitor 19 and the capacitor will now begin to discharge through the resistors 18 and 17. The voltage drop developed across resistance 18 by the discharge current will forward bias the transistor 11, thereby rendering the transistor 11 conductive.

The charge of capacitor 19 forces a current through transistor 11 and load 13, thereby actuating the print solenoid for the print mechanism which is identified as load 13.

To terminate the drive pulse, the base of transistor is returned to a negative condition which renders it conductive and again places the voltage V1 across the transmission lines 14 and 15. Since the capacitor 19 had partially discharged, a charge current again flows to re-charge the capacitor 19 to approximately the potential of V1. The voltage drop developed across the resistance 18 causes the transistor 11 to be rendered nonconductive so as not to affect the re-charging of capacitor 19. The circuit herein described substantially increases the energy capable of being delivered to the coil of a print device with an intended possibility of lowering the potential of the supply voltage V1 or otherwise increasing the distance of the transmission lines 14 and 15.

Referring to FIG. 2, there is shown an improved version of the high energy line driver which enables a substantial reduction in the potential required for potential source V2, while still having the capability of delivering the same magnitude of energy to the print device as described for the circuit of FIG. 1.

Referring to FIG. 2, when in the stand-by condition, the transmitter station maintains an up level at point 20 which causes transistors 21 and 22 to remain in an on codition. A continuous current flows from the potential source V2 over the lines 14 and and through resistor 23 maintaining a nominal voltage potential across resistor 23. Capacitor 24 is charged to approximately the potential V2 and remains charged as long as transistor 22 is conductive. Transistors 25 and 26 remain in an off condition since there is no potential difference across their base-emitter juctions.

When there is a pulse initiation by the transmitter station, it switches point to down level which turns off transistor 21 and, therefore, transistor 22. Transistor 22 in turning off removes the potential V2 from the lines 14 and 15 and allows capacitor 24 to discharge through the resistances 27, 28 and 23. The voltage drop produced by the discharge current through the resistors 27 and 28 forward biases the base-emitter junctions of transistors and 26. Transistor 26 switches the potential across capacitor 24 for application directly across the load 13, and at the same time, the current flows through transistor 25 and resistance 29 is sufficient and supplies the necessary base current for transistor 26.

When the transmitted pulse is terminated, this returns point 20 to the up level which turns transistors 21 and 22 to an on condition and restores the application of potential V2 across the lines 14 and 15. Since capacitor 24 will partially discharge during the pulse time, it now re-charges to the potential of V2. The voltage drop across resistors 27 and 28 produced by the charge current reverse biases the base-emitter junctions of transistors 25 and 26. Transistors 25 and 26 become nonconductive and, therefore, the only current through load 13 is a circulating inductive current which decays rapidly due to the Zener effect of diode 30. The purpose of diodes 31 and 32 is to minimize the charge time for capacitor 24. A negative feedback potential to transistor 22 is developed across resistor 33 by the charge current which limits the maximum line current to approximately three hundred milliamperes in the preferred embodiment.

Referring to FIG. 3, a timed pulse generated at the terminal can be used to gate energy to load 13 after the transmitter has conditioned the terminal. A variable reluctance magnetic pickup coil 34 is used as a voltage source to trigger a silicon-controlled rectifier 35. In order for 35 to conduct, it must have anode voltage supplied by transistor 25 in the manner described in reference to FIG. 2; and it must be forward biased, base-toemitter, as determined by 34.

In order to render 35 nonconducting, the transmitter must re-charge the line which extinguishes the anode voltage. The silicon-controlled rectifier 35 will remain nonconducting until its anode voltage is re-applied, despite continuous triggering of its base-emitter junction.

What is claimed is: 1. Remotely controlled switching system circuitry comprising:

(a) a transmitting station having:

(1) a voltage source, (2) a pulse-controlled switching device, (b) a transmission line coupling the transmitting station with (c) a receiving station having:

(1) an energy-storing device, (2) a charging circuit for the energy-storing device,

(3) a load,

(4) a first discharge circuit for the energy-storing device,

(5) a remotely controlled switching device coupled with said first discharge circuit,

(6) a second discharge circuit including the load,

the energy-storing device and the remotely controlled switching device.

2. Remotely controlled switching system circuitry as defined in claim 1 further characterized by and wherein response to the absence of a control pulse applied to the pulse-controlled switching device, the energy-storing device is charged approximately to the potential of the voltage source and through the medium of a control pulse applied to the pulse-controlled switching device, the charging circuit is disconnected and the current flow in the first discharge circuit controls the remotely controlled switching device and renders the second discharging circuit conductive thereby energizing the load from the energy-storing device.

3. Remotely controlled switching system circuitry as defined in claim 2 wherein the charging circuit for the energy-storing device includes at least one unidirectional current flow device to control the current flow in the charging and second discharging circuits.

4. Remotely controlled switching system circuitry as defined in claim 3 wherein the switching devices are transistorized.

5. Remotely controlled switching system circuitry as defined in claim 4 wherein the transmission line coupling the transmitting station and the receiving station is a two-line conductor possessing predetermined impedance characteristics.

6. An electrical circuit system adapted for the transmission of high energy pulses to a remotely located load through the medium of charging a capacitor and then by remotely controlled switching to discharge the capacitor into a load, the system comprising, in combination:

(a) a transmitting station having:

(1) a potential source,

(2) transistorized switching circuitry,

(b) a transmission line coupling the transmitting station with,

(c) a receiving station having:

(1) an energy-storing capacitor,

(2) a charging circuit for the energy-storing capacitor,

(3) a load device,

(4) a first discharge circuit for the energy-storing capacitor,

(5) a remotely controlled transistorized switching circuit coupled with said first discharge circuit and controlled thereby,

(6) a second discharge circuit including the load, the energy-storing capacitor and the remotely controlled transistorized switching devices.

7. An electrical circuit system as defined in claim 6 where in response to control pulses applied to the transistorized switching devices at the transmitting station, the energy-storing capacitor is charged to approximately the potential of the potential source and through the medium of another control pulse applied to the pulsecontrolled transistorized switching devices at the transmitting station, the charging circuit is disconnected and the current flow in the first discharge circuit renders the second discharge circuit conductive thereby energizing the load device from the energy-storing capacitor.

8. An electrical circuit system as defined in claim 7 wherein the charging circuit for the energy-storing capacitor includes at least one unidirectional current flow device to control the current flow in the charging and second discharging circuit,

6 References Cited UNITED STATES PATENTS 2,421,022 5/ 1947 Francis.

2,484,352 10/ 1949 Miller.

3,080,487 3/1963 Mellott 340--167 3,392,374 7/1968 Grace 340167 HAROLD I. PITTS, Primary Examiner US. 01. X.R. 

